1. Field of the Invention
This invention relates generally to E9-1-1 emergency phone calls. More particularly, it relates to handling emergency E9-1-1 calls using Voice Over Internet Protocol (VoIP).
2. Background of the Related Art
Voice Over Internet Protocol (VoIP) is a technology that has been developed as an alternative packet-based telephony technology to the conventional switched telephony service (e.g. PSTN). VoIP takes advantage of high speed Internet data networks, and is able to provide low cost telephony services to end users. VoIP technology emulates a phone call, but instead of using a circuit based switched system such as the telephone network, utilizes packetized data transmission techniques most notably implemented in the Internet.
VoIP phone calls are routed to a VoIP voice gateway, from which they are passed on to their destination VoIP device. Conventional VoIP voice gateways (i.e., soft switches) are typically located in only a few places across the country. A soft switch is a programmable network switch that can process the signaling for all types of packet protocols. Also known as a ‘media gateway controller,’ call agent,' or ‘call server,’ such devices are used by carriers that support converged communications services by integrating signaling system No. 7 (SS7) type switched telephone signaling with packet networks. Softswitches can support, e.g., IP, DSL, ATM and frame relay.
Because VoIP is Internet Protocol (IP) based, call related information such as CallerID type services may not be available or accurate. A location of a given VoIP device may be statically provisioned to be at a given geographic location, or queried from a home location register (HLR) in a mobile system.
911 is a phone number widely recognized as an emergency phone number that is routed to emergency dispatch personnel and used to determine a location of a caller. Enhanced 911 (E911) is defined by the transmission of callback number and location information to the relevant public safety answering point (PSAP). A PSAP is the endpoint of an emergency services call. PSAPs are responsible for answering emergency services calls. E911 may be implemented for landline and/or mobile devices. Some Public Safety Access Points (PSAPs) are not enhanced, and thus do not receive the callback or location information from any phone, landline or mobile.
The problem is not necessarily solved with the use of a centralized emergency call center. In such case, when a VoIP customer places an emergency call such as an E911 call, the call may be routed to an emergency call center that is very far away, and in some instances half-way across the world to reach the centralized emergency call center. The VoIP E911 call must then be transferred to the relevant 911 center (public safety access point (PSAP)). However, this transfer must take place over the Public Switched Telephone Network (PSTN) because such transfer cannot conventionally be gained to the PSAP's existing Enhanced 911 (E911) dedicated network where location and callback number of the originating 911 caller are provided. Moreover, note that even the call related information (e.g., CallerID) provided with the call would relate to the identity and location of the centralized call center—not to the callback number and certainly not the location of the customer originally dialing 911.
FIG. 7A shows conventional relevant systems in an emergency 911 call made via a wireless caller in a GSM network.
In particular, as shown in FIG. 7A, a wireless GSM caller 190 dials 911. The 911 call is serviced by a cell site of a service provider, which includes a given mobile servicing center (MSC) 402. The MSC 402 performs a query of a
PSAP Automatic Location Identification (ALI) database 406 via a gateway mobile location centre (GMLC) 432 to determine a unique 10-digit phone number of the proper local PSAP physically responsible for the location of the 911 caller 190.
FIG. 7B shows conventional relevant systems in an emergency 911 call made via a wireless caller in a CDMA or TDMA network.
In particular, as shown in FIG. 7B, a wireless CDMA or TDMA caller 190b dials 911. The 911 call is serviced by a cell site of a service provider, which includes a given mobile servicing center (MSC) 402. The MSC 402 performs a query of a PSAP Automatic Location Identification (ALI) database 406 via a mobile positioning center (MPC) 707 to determine a unique 10-digit phone number of the proper local PSAP physically responsible for the location of the 911 caller 190b. 
As technology progresses, dual mode wireless phones have emerged. A dual mode wireless phone is one that operates using CDMA or GSM technology when out on the open road, but which switches to a local area network such as a Wireless Fidelity (WiFi) network when within range at home or in the office. For instance, a wireless phone may join a WiFi network created in a home or office used by a wireless computer network, when within range of that WiFi network, to gain access to the Internet and thus communicate using voice over Internet Protocol (VoIP). Thus, dual mode phones operate as an ordinary cell phone as a mobile user traverses a cell network (e.g., a CDMA network), until you get home or to your office containing a WiFi network, at which time the cell phone drops use of the CDMA network and instead switches over to use of the WiFi network.
When a wireless phone is mobile and away from home or the office, latitude/longitude location information is pretty much the best that can be provided. However, when within a home or office on a WiFi network, it is preferable that more accurate location information such as MSAG format location information including street address be provided instead of merely lat/lon type location information.
Unfortunately, provision of MSAG format location information along with a WiFi wireless call presents significant expense to a wireless carrier. Instead, without change to the wireless carrier's network, lat/lon location information is the best that can be provided in all cases, even when the wireless dual mode phone is communicating over the Internet using a WiFi network.
FIG. 8 shows one conventional solution to delivery of location data in wireless E911 format, but providing only latitude/longitude (lat/lon) location information.
In particular, as shown in FIG. 8, a wireless caller 190 using a dual mode phone dials 911.
A user agent 180 provides service to the wireless VoIP device 190 so that the dual mode phone is provided with wireless Internet access. (“User agent” is a common name for a device that makes a VoIP call, e.g., a SIP phone, Skype™ on a Personal Computer, etc.)
The call then progresses over the Internet (Voice Over Internet Protocol (VoIP)) via a wireless fidelity (WiFi) access point 170. A WiFi access point 170 is, e.g., a wireless local area network hub in a house or office. The WiFi access point 170 provides Internet access to the wireless dual mode phone 190 typically via a wired connection to the Internet. (While described with respect to WiFi, the invention as described below relates equally to later embodiments of local area network hot spots (e.g., WiMAX, etc.).
A wireless VoIP base station controller 160 communicates with the WiFi access point 170 to provide circuit switched, time-division multiplexing (TDM) access to the VoIP call.
The user agent 180, WiFi access point 170 and a Wireless VoIP base station controller 160 use TCP/IP transport and session initiation protocol (SIP) protocols.
From the wireless VoIP base station controller 160, the VoIP E911 call is passed to a mobile switching center (MSC) 800. If part of a CDMA network, the MSC 800 passes an Origination Request (ORREQ) message (IS-41) to a 3rd Generation Partnership (3GPP2) mobile positioning center (MPC) 802 per the 3GPP2 joint standard #36 (J-STD-036). The ORREQ starts the process where location is ultimately obtained from a Position Determination Entity (PDE). The PDE consumes, or uses, the location information itself.
If part of a GSM network, the MSC 800 passes a subscriber location report (SLR) request to a Gateway Mobile Location Center (GMLC) 802. An SLR is a push of location. Thus, location is actually obtained before the message is sent. In such a GSM network, the MSC 800 actually gets the location back from the network element (SMLC) on the time division multiplex (TDM) side. The MSC 800 then provides the location to the GMLC 802.
The VoIP E911 call is then directed to a selective router 140 serving the designated public safety access point (PSAP)/911 network 195 for the determined lat/lon location.
FIG. 9 shows a conventional delivery of location data in MSAG format for VoIP calls for processing E911 calls using the NENA approved i2 call flow.
In particular, as shown in FIG. 9, a dual mode phone user 190 makes a 911 call over their WiFi network as otherwise described in FIG. 8. For instance, the VoIP E911 call is serviced by a user agent 180, a WiFi access point 170, and a wireless VoIP base station controller 160, as otherwise shown and described with respect to FIG. 8. However, in the embodiment of FIG. 9, the wireless carrier is a voice service provider network 900, enjoying the benefits of a VoIP network.
The voice service provider network 900 passes a SIP invite message to a VoIP positioning center 904. The SIP invite is used to get location information from the VPC 904. In this scenario, location is determined by the VPC 904, and the VPC 904 is used to make decisions based on that location. In particular, the VPC 904 sends signaling to the VSP 900 so that it can get the call to the right PSAP 195, but the location information itself is not sent back to the VSP 900. Rather, just signaling codes necessary to route the VoIP E911 call to the proper selective router 140 and PSAP 195 (via an emergency services gateway 902) are sent from the VPC 904 to the VSP 900. (An emergency services gateway (ESGW) is typically a function inside a standard media gateway. A media gateway is typically TCP/IP on one side, and TDM trunks on the other side.)
Location information itself in the embodiment of FIG. 9 is maintained in a subscriber line database (SLDB), created from an out-of-band transaction. This means that the dual-mode phone user 190 presets their MSAG format location into the SLDB, e.g., by logging into a suitable SLDB portal during registration of their dual-mode phone, and enters their location (e.g., relevant street address). The PSAP 195 accesses this MSAG quality location information using a automatic location identificatier (ALI) query to the VPC 904, which in turn pulls location data from the SLDB, formats it, and provides it back to the PSAP 195.
Trials have been conducted in which a local exchange carrier (LEC) has permitted access to a selective router for the E911 network via the PSTN. In this trial, the LEC designated a specific 10-digit telephone number. A caller has their emergency call transferred to this 10-digit telephone number, which is then call-forwarded within the central office to the selective router, which then forwards the call to the correct PSAP based upon the digits dialed. However, this solution suffers the same significant drawbacks as that shown in FIG. 7, i.e., that callback number and location are not provided to the responsible PSAP.
Thus while carriers continue to accommodate and indeed foster development of a nationwide VoIP telephone network, difficulties nevertheless abound, particularly with respect to provision of location of a VoIP caller to an emergency response center. As a result, wireless carriers wishing to offer dual-mode phones to customers must make significant technology investments and infrastructure upgrades to handle VoIP calls. (Dual-mode phones are capable of initiating mobile E9-1-1 calls using, e.g., Global System for Mobile Communications (GSM) or code division, multiple access (CDMA), or even wireless fidelity (WiFi)). The desire is to handle use of such technologies in a VoIP communications network. However, the reality is that many wireless carriers continue to utilize switched technology equipment at least at the front end in communication with a VoIP caller. If an E911 call is placed, it is likely handled in the wireless carrier's network from a circuit switched interface. The present inventors realize that this causes a delay in the introduction of VoIP technology, and reduced competition from other carriers. Moreover, full compliance with national requirements may not be possible, e.g., the need to provide location and callback information.
There is the need for a simple and effective solution to providing easy and full access to the Enhanced 911 network of an emergency services provider (e.g., PSAP) from wireless VoIP users of a carrier utilizing a switched network.